I have a 4 year old female miniature schnauzer. In the recent months she has been urinating on the carpet at night. Last night I took her out at 10 p.m., and at 11 p.m. she scratched on my door to take her out, but she had already gone on the carpet. Can there be a medical explanation. Do dogs get urinary infections? Should I contact my vet for an appt??? Lisa.